BOURDEAU, P.E.*; PADILLA, D.K.*; Stony Brook University; Stony Brook University: �Might as well jump� � Inducible dispersal in response to environmental cues in two species of Littorine snails

For many organisms, the ability to assess and respond to cues from the surrounding environment has important fitness consequences. In particular, the ability to disperse from a less favorable habitat can mean the difference between life and death. Snails in the genus Lacuna live in two different habitat types, on macroalgae on rocky shores or on epiphyte covered eelgrass. Snails disperse among habitats. Dispersal behavior (jumping) consists of lifting the foot off of the substratum and secreting a mucus parachute, facilitating passive transport in a current. We tested whether dispersal behavior was influenced by recent feeding history and cues associated with predation risk for two sympatric species, L. vincta and L. variegata. We conditioned snails for 10 weeks by feeding them either epiphytes on eelgrass in tanks full of eelgrass, or the green alga Ulva in tanks containing Ulva. Conditioned snails were placed in a large flume on either macroalgae (the kelp Neriocystis) or eelgrass. The water was slowly accelerated to approximately 20 cm/sec. and the snails were observed for a maximum of 5 minutes. Snails mismatched to their feeding habitat jumped more often and sooner than snails matched to their feeding habitat. L. variegata jumped more often in the presence of cues associated with some predators (a sea star, fish, but not a crab) and in response to crushed conspecifics. However, L. vincta dispersed more only in response to cues associated with fish. These results are evidence of an inducible dispersal response to unfavorable feeding habitat and predator risk. Variability among species and among individuals within species in the propensity to jump suggests differences in the ecology and evolutionary history of the two species and possibly genetic differences among individuals for this behavior.